You can use the SOLIDEDIT command to remove redundant faces, edges, and vertices from a 3D solid automatically, and check to make sure that the 3D solid is valid.
You can remove edges or vertices if they share the same surface or vertex definition on either side of the edge or vertex. The body, faces, or edges on the solid object are checked, and adjacent faces that share the same surface are merged. All redundant edges, imprinted as well as unused, on your 3D solid object are deleted.
You can check to see if your solid object is a valid 3D solid object. With a valid 3D solid, you can modify the object without incurring failure error messages. If the 3D solid is not valid, you cannot edit the object.